The letter read in part: "Dear Mike Ashley. We are writing to urge you to do what is right for Newcastle United this month and we hope, for a change, you are willing to listen to us and act accordingly.

"This is a critical month for the football club, both in terms of your stated desire to sell and the need to strengthen the squad, as repeatedly requested by the manager Rafa Benitez.

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Highlights from Manchester United's win against Newcastle in the Premier League

Highlights from Manchester United's win against Newcastle in the Premier League

"We are hoping you see the sense in striving to do both, but if you cannot find a suitable buyer, then it is imperative that you still release the funds needed to improve the squad.

"To fail to do so, would seem both reckless and foolish given the damage you know relegation will do. The ongoing takeover cannot be used an excuse not to spend money in the January transfer window.

"If you refuse to spend money this month, the risk of relegation not only increases, it will also mean the manager will not sign the new contract you have offered to him.

Newcastle fans are concerned that manager Rafa Benitez might leave the club if he is not given funds to spend on new players

"You have repeatedly said that you want Benitez to stay, so do the things needed to make sure that happens. In short, back him and give him what he needs in this window.